The present invention is directed to insulated air ducts and, in particular, to flexible insulated air ducts wherein the fibrous insulation is helically wrapped about the flexible core of the air duct and the air duct is formed in one continuous operation.
Insulated, flexible air ducts are in common use in commercial, industrial and residential heating, ventilating and air conditioning systems. These air ducts typically comprise a cylindrical flexible core having a wire helix with spaced convolutions enveloped in a plastic film. The flexible core is surrounded by a layer of fibrous insulation, such as glass fiber insulation and a vapor barrier jacket or sleeve of plastic film envelops the fibrous insulation.
Under present practice, flexible, cylindrical, tubular cores (typically in pre-cut twenty-five foot sections), rolls of fibrous insulation blanket and jacketing material are shipped separately to a fabrication shop where the flexible, insulated duct is assembled in sections (typically twenty-five feet in length), packaged and forwarded to either distributors or heating, ventilating and air conditioning contractors. At the fabrication shop, the rolls of fibrous insulation blanket, which have been sized to widths corresponding to the circumferential dimensions of the various diameter tubular cores being insulated and jacketed to form the flexible insulated air ducts, are hand or mechanically wrapped about the tubular cores forming one longitudinally extending seam along the length of each section of air duct as shown in U.S. Pat. No. 4,410,014; issued Oct. 18, 1983; to Owens-Corning Fiberglas; and entitled "Flexible Insulated Air Duct". At the time of assembly, a jacket of vapor barrier material is placed over the layer of fibrous insulation to complete the fabrication of the air duct section. If required, a layer of scrim material can also be interposed between the layer of fibrous insulation and the tubular core or between the layer of fibrous insulation and the jacket for additional strength.
The current practice of shipping the separate components of the flexible, insulated air duct to a fabrication shop and assembling the flexible, insulated air duct at the fabrication shop is labor intensive, requires the maintenance of an inventory of separate widths of insulation and jacketing for each different duct diameter, and is relatively costly. Thus, there is a need to reduce the separate packaging, shipping, handling and inventory costs involved in the present practice of assembling flexible insulated air duct at a fabrication shop and the labor intensive assembly procedures currently used by such fabrication shops.